Method of bending strip containing inflatable passageways



United States Patent [45] Patented [73] Assignee Richard A. Shive Madison, Illinois 709,636 March 1, 1968 Dec. 8, 1970 Olin Corporation a corporation of Virginia [72] Inventor 21 Appl. No. [221 Filed [54] METHOD OF BENDING STRIP CONTAINING INFLATABLE PASSAGEWAYS 16 Claims, 8 Drawing Figs.

[52] 0.8. CI. 113/118, 29/l57.3 [51] lnt.Cl 821d 53/02 [50] Field ofSearch 29/l57.3(V), 157.3(D), (RB); 1 13/1 l8(V), l 18(D) [56] References Cited UNITED STATES PATENTS 2,850,793 9/1958 Schwelleretal 2,949,664 8/1960 Pauls 29/] 57.3 2.994946 8/196] Reyn0lds..... 29/157.3 3,133,517 5/1964 Brick et al. 29/157.3X

Primary Examiner-John F. Campbell Assistant Examiner-D. C. Reiley An0rneysilenry W. Cummings, Robert H. Bachman,

Richard S. Strickler and George J. Koeser ABSTRACT: A process of bending strip containing at least one inflatable passageway which comprises embossing the strip to provide grooves in corresponde'ncetdthe passageway in the strip. The strip may be bent during the embossing or subsequent thereto to any desired angle, with the bending taking place in the region of the embossment. Following the bending operation, the passageways in the strip are inflated. By using this process, it is possible to eliminate kinking of the inside radii of the inflated tubular passageway and also eliminate the reduction in tube height of the outside radii of the tubular passageway.

PATENTEU 0pc 81970 SHEEI1UF3 INVENTOR RAQMARD/LShMME ATTORNEY PATENTED DEC 8I97U sum 3 or 3 INVEN'I'OR RICHARD/4. SH/VE fashion.

gages the portion 33 of the center spindle shown METIIOD OF BENDIN G STRIP CONTAINING INFLATABLE PASSAGEWAYS containing the stop-weld material to at least one other sheetat all places except where the stop-weld has been placed. After the bonding, the passageway pattern defined by the stop-weld material may be inflated to form passageways.

It is often convenient to inflate such passageways in strip material and to bend the strip material into long serpentine shaped structures which have heat exchange application.

However, if a radius below approximately. 1 inch is bent, their results kinking in the inside radii of the tube and a reduction in tube height on the outside radii of the tube is evident. This is generally the case in tube wall thicknesses less that 0.030 inches. Kinking is disadvantageous because if the expanded passageways contain kinks, a higher pressure drop oc curs.

Furthermore, the kinking may be sufficiently severe to cause failures in the material. For instance, for condenser applications pressures up to .3,000'p.s.i. must be tolerated in the passageways. Evaporatorpressures up to 1,200 p.s.i. must be tolerated. h

Thus, it is an object of the present'invention to avoid kinking which often occurs during bending in a conventional It is another object of the present invention to avoid kinking when bending strip at a radius of less than 1 inch. h

It is another object of this invention toemboss and bend tube wall thicknesses below 0.030 inches without kinking.

It is another object of the present invention to provide a method and apparatus for bending strip to be used in serpen-' tine shaped heat exchangers i It is another object of this invention to provide a method of bending strip whereby fin material can be placed between the bent strip and then inflated toform heat exchangers.

Other objects will be apparent from the followingdescriptions and drawings. i t h FIG. 1 is a schematic perspective view of the apparatus and process of the present invention.

FIG. 2 is a sectional view of the center spindle assembly which is used in the apparatus of the present invention.

FIG. 3 is a perspective view of the movable baseplate and divider blocks.

FIG. 4 is a perspective view of the roller assembly.

FIG. 5 is a perspective view of the follower block and pins which may be utilized in the present invention.

FIG. 6 is a perspective view of strip material which has been bent and formed according to the present invention.

FIG. 7 is a perspective view of strip which has been bent according to the present invention, fin material placed between the strip, and the strip inflated to form a heat exchanger.

FIG. 8 is a schematic view of an exemplary. process sequence which may be utilized according to the present invention.

In FIG. 1 there is shown a fixed base plate 10 upon which is mounted a movable base plate 20. Passing through the movable base plate is a center spindly-spindle 30. As shown in FIG.

1 2, this center spindle has an enlarged portion 31 which engages the fixed base plate at 11 by a press fit. Holes 12 are provided for mounting the fixed base plate upona large table,- floor, etc. The movable base plate through opening 21, en-

witha sliding v fit. h A die spindle 40, having grooves 41, 42, 43 and and a shoulder 45 is placed upon the center spindle through center opening 49. It can be seen from FIG. 1 that the center spindle The threaded portion 53 passes through divider blocks 60 .through openings 63and 64 therein. As shown in FIGS. land 3, the divider blocks are bolted to the rotating base plate, into openings therein with bolts 61. The divider blocks are bolted at 62 to guide top 80 containing a generally elliptical opening 81 therein. There is a corresponding opening 23 in the movable base plate.

The adjusting bolt unthreaded portion 54 also passes into a roller fixture 70 shown in FIG. 4. This roller fixture comprises upper and lower plates 71 and 72 respectively, each having openings 73 and 74 therein. These plates are bolted at 77 (or otherwise attached) to back block 75. Circular end portion 54 of the adjusting bolt fits into opening 76, but opening 76 is made sufficiently large that end portion 54 may be easily removed therefrom.

Mounted between the plates 71 and 72 is a wiper roller 90. A wiper roller pin 91 passes through. the center of the wiper roller and into the elliptical openings 81 in the guide top and 23in the movable base plate. Clearance, for example, about two-thousandths of an inch is provided between the guide top '80 and the upper plate 71 and also between the plate 20 and the lower roller fixture plate 72. Also, lubricationis generally provided so that the roller fixture assembly 70 and wiper roller 90 can move back and forthon the plate 20 by rotation of adjusting bolt 50.

Mounted on the base plate 10 is a clamping block 100 shown in detail in FIG. 1. This clamping block is made in two halves, the stationary clamp block 101 and the movable clamp block 102. A socket head capscrew 103 holds the fixed half 101 in place on the fixed base plate 10., Bolt 104 passes through respectively openings 106 and 107. Both the halves contain cooperating recessions 110 and 111 for processing inflated strip.

" Follower block 120 shown in FIG. 5 contains a plurality of grooves 121, 122, 123 and 124. There: is also provided a recess are provided on die spindle 40 and follower block 120.

' A retainer strap 130 is also provided, having an opening 131 which opening allows placement of the strap upon the nut 46.

After placement of the nut 46 on the die spindle 40, the

strap 130 may be placed over shoulder 47 and resting on the die spindle and guide top 80. The opening 131 provides a bearing surface during rotation around the die spindle.

The retainer strap has a second opening 132 through which passes a locking T140. The T in engagement fits into an opening 82 in the guide top 80.

l Two adjustable screws are also screwed into threaded holes 24 in the movable plate 20 to regulate the height of strip to beprocessed in the apparatus.

In operation, a piece of strip S which contains stop-weld at appropriate places is fed throughclamping block 100 and is placed upon the adjustable screws 150. The height of the adjustable screws 150 is adjusted so that the areas in the strip corresponding to desired passageways which contain stopweld are in alignment with the pins I26 on 126a or the follower block and the grooves 4144 onthe die spindle. The strip is clamped in the clamping block by tightening bolt 104 at a point whereby the bend will occur at the die spindle at the desired length of the strip. One side of the strip contacts die spindle 40. The follower block 120 and pins are then brought into contact with the other side of the strip. Also, at this point, the retainer strap 130 is engaged upon the die spindle nut 46. The locking T 140 is inserted into opening 132 in the retainer strap and into the opening 82 in the guide top.

The adjusting bolt 51 is rotated to urge the wiper block 90 into firm engagement with the follower block. For manual operation, a crescent wrench may be utilized to rotate the adjusting bolt 51, to insure firm engagement of the wiper roller 90 and follower block 120 with pins 121-124.

At this point, the entire movable assembly is rotated with respect to the fixed plate (clockwise in FIG. 1) around the die spindle 40 for at least 25 and preferably 90 to 360. This, of course, bends the strip. For example, as indicated in FIG. 6, the strip 200 is bent 180. However, it also provides grooves 202 in the strip corresponding to the points on the strip where passageways are to be inflated.

Upon inflation of the passageway no kinking is observed in any size radii including radii below 1 inch. FIG. 7 shows the inflated strip, with passageways 302 corresponding to grooves 202 in FIG. 6.

After the strip has been bent, for example, into a serpentine pattern by the bending just described, for many applications it is desirable to braze or otherwise place fin material between the strip. Such fin material is shown at 310 in FIG. 7.

FIG. 8 shows an exemplary strip processing sequence. The previously described bending takes place at schematically shown bending station 400. The strip will leave the bending station 400 and pass to the assembly station 410. At this point, the fin material 411 and endplates 413 and headers 414 are assembled. The fin material and/or the strip will contain a coating of brazing material so that when the strip-fin units 412 are introduced into the furnace 420, which is maintained at the temperature appropriate for the particular brazing alloy, strip material and fin material being processed, the fin material is solidly brazed to the strip.

After the brazing operation, the articles are then moved on to the inflation station 430. At the inflation station at one end of the strip an inflation needle is introduced into the pattern of stop-weld material, and clamped by means of hydraulic line 432. Fluid pressure by means of air line 431 which, for example, supplies water or air, is then introduced into the opening and the passageway pattern is inflated to form passageways corresponding to the passageways of stop-weld material between the sheets. If desired, the inflated articles may be checked for leaks in a water tank 440.

Inflation subsequent to the brazing operation provides very intimate contact between the fin material and the strip so that the brazed fin material is in excellent heat exchange relation with the strip.

It is to be emphasized that the bending according to the present invention need not be used in connection with brazed fin applications only. For example, the strip could be provided with fin area in accordance with Keith application, Ser. No. 630,376, now abandoned, assigned to the same assignee as the present application.

It also is to be emphasized that the number of corresponding pins 126 and grooves 4144 may vary as desired. There have been shown four for purposes of illustration but, if desired, one only, or a great many grooves and corresponding pins may be provided in accordance with the number of passageways in this strip.

Other fastening methods, such as welding, could be used instead of screws.

Also, instead of a die spindle, a rubber pad could be used to cooperate with pins 123 or other protrusion.

It is also to be emphasized instead of the follower block, the wiper roller could be contoured so as to contain the equivalent of pins 126 in the follower block. Thus, with this construction, the follower block would be eliminated. Additionally, the embossing and bending could be carried out separately, but it is I generally more convenient to carry them out simultaneously.

The bending operation of the present invention may be carried out continuously. This may be done in the following manner.

Strip is fed into the apparatus at a continuous intermittent rate after a desired amount of strip has passed the clamping block. The clamping block may be made to close automatically with an appropriate electroneumatic time sequence or, the bending and embossing could take place while the strip is moving. Likewise, either the follower block or an appropriately contoured wiper roller may be automatically moved into engagement with the strip and the die spindle 40. Appropriate electroneumatic power would then rotate the movable plate around the die spindle.

Such automatic control and time power sequence are wi well known to those skilled in the metal fabricating field. However, such automatic operation would nonetheless produce bended strip free from kinks, which is the essence of the present invention.

It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modifications of form, size, arrangement of parts and detail of operation, but rather is intended to encompass all such modifications which are within the spirit and scope of the invention as set forth in the ap pended claims.

I claim:

1. A process for bending strip containing at least one inflatable fiuid passageway comprising: embossing said strip to provide at least one groove in said strip substantially corresponding to the area in said strip where said at least one passageway is to be inflated; bending said strip to a desired angle'in the area of the embossment; and inflating said passageway in said bent and embossed strip.

2. A process according to claim 1 in which the passageway is defined by a pattern of stop-weld material.

3. A process according to claim 1 in which the passageway is defined by welded tubing.

4. A process according toclaim 1 in which the passageway is defined in seamless tubing.

5. A process according to claim 1 in which the strip is held firmly prior to embossing.

6. A process according to claim 1 in which said embossing is obtained by using a member having a deforming protrusion which cooperates with a member having an appropriately dimensioned groove to emboss the strip in the area of said at least one passageway to the shape of said protrusion.

7. A process according to claim 6 in which said member having an appropriately dimensioned groove is a rubber pad.

8. A process according to claim 1 in which the strip is bent at least 25 9. A process according to claim 8 in which the strip is bent from 360.

10. A process according to claim in which said embossing and said bending takes place simultaneously.

11. A method according to claim 1 in which said process is carried out continuously.

12. A process according to claim 1 in which said strip is bent at a radius of less than 1 inch.

13. A method according to claim 1 in which fin material is brazed onto said bent strip before said strip is inflated.

14. A process according to claim 13 in which said strip is bent into a serpentine pattern prior to brazing on the fin material.

15. A process according to claim 1 in which after said strip is bent, the strip is treated to increase its surface area.

16. A process according to claim 15 in which edge portions of said strip are bent to provide greater surface area. 

